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starship-design: FW: SpaceViews -- 1999 August 8

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Subject: SpaceViews -- 1999 August 8

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                            S P A C E V I E W S
                             Issue 1999.08.08
                               1999 August 8

*** News ***
	House Delays Consideration of NASA Budget
	DS1 Reveals Asteroid Origins
	New Computer Installed on Mir
	Britain Funds Mars Lander, Other Projects
	Ariane Launch Delayed
	Chandra Approaches Final Orbit
	Human Error Blamed for Recent Launch and Satellite Accidents
	Scientists Salvage Useful Data from Failed Satellite
	SpaceViews Event Horizon
	Other News

*** Articles ***
	The Early Explorers

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    *and Hubble Space Telescope apparel are just some of the new* 
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    *             http://www.countdown-creations.com            *

                             *** News ***

              House Delays Consideration of NASA Budget

	NASA won a reprieve -- or perhaps a stay of execution -- this
week when Congress decided to delay consideration of a budget bill
until after an August recess.

	The full House of Representatives was scheduled to debate and
vote this week on HR 2684, an appropriations bill for the Departments
of Veterans Affairs and Housing and Urban Development as well as
independent agencies.  The bill had been approved by the House
Appropriations Committee July 30.

	However, the House delayed consideration of the bill until
after its August recess, which begins August 6, out of consideration
for Rep. Alan Mollohan (D-WV), the ranking minority member of the
appropriations subcommittee responsible for the bill.  Mollohan's
father passed away earlier in the week.

	This means the bill will not be taken up by the full House
until they return from recess in September, giving lobbyists and
activists more time to call for the restoration of funds cut by the
current version of the bill, or to call for additional cuts.

	HR 2684 would give NASA a budget of $12.7 billion in fiscal
year 2000, starting October 1 of this year.  That would be $1 billion
below its current budget and $900 million below the original proposal
for FY 2000 submitted by President Clinton.

	A House appropriations subcommittee slashed more than $1.3
billion from NASA's 2000 budget during a markup session July 26,
including a $640 million cut -- nearly 30 percent -- from the
agency's space science budget.  The full appropriations subcommittee
restored $400 million to the space science budget in a July 30
hearing, but left other cuts intact.

	Dan Goldin, NASA administrator, claimed that the cuts would
force the agency to lay off or temporarily furlough workers, and
possibly close up to three NASA centers.  The cuts would kill a
number of planetary and space science missions and could further
delay assembly of the International Space Station.

	The cuts have mobilized grassroots activists, including
members of the National Space Society, the Planetary Society, and
other organizations, to contact Congress and call for restoration of
NASA funding.  "Their strong response, demonstrating public support
for the planetary program, has helped influence Congress," claimed
Lou Friedman, executive director of the Planetary Society.

	These organizations plans to keep the heat on during the
recess. "The message to Congress from The Planetary Society is 'No
more cuts to NASA, please vote against any bill that cuts the NASA
budget,'" the organization said in a statement.

	The Senate has yet to act on any appropriations legislation
for NASA, and will not do so until after the August recess. 

                     DS1 Reveals Asteroid Origins

	While failing to return high-resolution images of asteroid
Braille, NASA's Deep Space 1 (DS1) spacecraft returned data of
arguably far greater value: clues to the origin of the asteroid.

	Infrared spectra taken by an instrument on DS1 showed that
Braille very closely resembled the large main-belt asteroid Vesta,
and may well be a chunk of Vesta blown off in a collision millions of
years ago.

	During a press conference August 3, mission scientists said
the spectra of Braille at near-infrared wavelengths closely matches
the spectra of not only Vesta itself, but meteorites on Earth that
have been linked to Vesta as well.

	The findings were "astounding and surprising" said Robert
Nelson, project scientist.  "It's truly exciting."

	Another scientist involved with the mission, Larry Soderblom,
called the results a "scientific surprise."  The comparison of the
spectra between tiny Braille and the far larger Vesta "is a
remarkably close match," he said.

	Vesta is unique among the major asteroids in that it has a
surface of basaltic rock that appears to have formed from volcanic
activity early in its history.  Hubble Space Telescope images have
shown evidence for a large impact basin on the asteroid.

	Vesta's composition is closely matched by a fraction of the
meteorites found on the Earth, however, it is difficult to get
material off Vesta, located in the main asteroid belt, to the Earth.
The conundrum was solved earlier this decade when astronomers
discovered a group of small asteroids -- "chips" off Vesta --
trailing away from the asteroid to a gap in the asteroid belt caused
by a gravitational resonance with Jupiter.  That resonance would be
able to fling asteroids that enter it into orbits that go through the
inner solar system.

	That would explain Braille, which is in an eccentric orbit
that crosses the orbit of Mars.  Scientists said the orbit will
gradually move closer to the Sun in the future, crossing the orbit of
the Earth in about 4,000 years.

	Deputy mission manager Marc Rayman provided some insight into
why the spacecraft was unable to return closeup images of Braille, as
it passed 26 km (16 mi.) from the surface of the asteroid.  When DS1
located the asteroid, it was some 400 km (250 mi.) off its predicted
position, because of uncertainties in the asteroid's orbit.  The
spacecraft performed a course correction to move closer, and was able
to keep track of the asteroid until 70 minutes before closest

	At that time DS1 switched to another navigation mode, but the
camera could not detect the asteroid, which was in shadow at the
time.  The spacecraft used the older, but less accurate, navigation
data, leaving the camera pointed in the wrong direction.

	As DS1 moved away, however, the asteroid was in sunlight
again and the infrared camera was able to take images from a range of
about 13,000 to 14,000 km (8,000 to 8,700 mi.), enough to show that
the asteroid has an oblong shape of 2.2 by 1 km (1.3 by 0.6 mi.)

	However, Nelson said, the dozen spectra were the key data
obtained by the spacecraft.  "Sometimes a spectrum is worth a
thousand pictures," he said.

                    New Computer Installed on Mir

	The crew of the Russian space station Mir took advantage of a
shutdown of a guidance computer over the weekend to install a new
version of that computer, Russian officials said Monday, August 3.

	The three-man crew on Mir had shut down their main guidance
computer when it malfunctioned on Friday, relying instead on a backup
system.  Unlike past computer failures, the backup systems kept the
station properly aligned so that the solar panels on Mir could
generate power.

	Turning off the main guidance computer, though, did shut off
power to some parts of the station, giving the crew a chance to do
maintenance activities not otherwise possible.  That included
installing a new guidance computer sent to the station last month on
a Progress resupply spacecraft.

	The new guidance computer is supposed to be less prone to
failures than the old system, meaning the station should be able to
maintain the proper attitude even when the current crew departs
August 28, leaving the station unoccupied.

	If the station were to lose attitude control while
unoccupied, it would be difficult to restore control and make a
controlled deorbit of the station, planned for early 2000, unlikely.

              Britain Funds Mars Lander, Other Projects

	The decision announced this week by the British government to
partially fund a Mars lander is part of a larger effort to develop a
national "space strategy", the nation's science minister said.

	Science Minister Lord Sainsbury announced August 3 a new
investment of #19.5 million (US$40.5 million) into several new space
projects, including #5 million (US$8.1 million) into the Beagle 2
Mars lander.

	"The Beagle 2 Mars Lander is an exciting scientific mission
which will be a superb demonstration of the skill and creativity of
British science and engineering," Sainsbury said in a speech at the
national Science Museum.

	The funds will be used to help develop the 60-kg (132-lb.)
lander, which will fly to Mars on the European Space Agency's Mars
Express orbiter spacecraft in 2003.  The lander will separate from
Mars Express shortly before arrival and land on the planet. 

	Once there, a camera on the lander will return images from
the surface, while a robot arm gathers rock and soil samples from
around the lander.  Instruments on the lander will look for evidence
of organic material, water, or minerals that may be evidence of past
or present life.

	The #5 million announced by the British government is only a
fraction of the #25 million needed to build the lander.  The
remainder of the funds will come from a public/private partnership
project officials are working to put together.  "The signal Lord
Sainsbury has sent today is that the government's behind us," said
Beagle 2 lead scientist Colin Pillinger of Open University. "This
gives us the chance to go to others and say 'will you commit?'"

	The funding announcement for Beagle 2 was just part of a
larger space strategy Sainsbury unveiled.  The "UK Space Strategy
1999-2001" maps out several broad objectives for the country's space
program: help industry with business opportunities, develop
innovative technologies, support earth and space science, and improve
communications with the public.

	Support for commercial endeavors was at the forefront of the
new strategy.  "Commercial markets for satellite communications and
navigation are estimated to reach $150 billion per year by 2010," he
noted.  To that end, most of the additional government investment in
space programs, #10.5 million (US$17 million), will go to an ESA
program to develop advanced telecommunications technologies.

	An additional #4 million (US$6.5 million) will be used to
fund the National Space Technology Program, an effort to develop new
spacecraft technologies, such as advanced thrusters under development
by Matra Marconi.

	Overall funding for British space efforts, which includes
space-related funding from a number of government departments, is
expected to total at least #180 million (US$291 million) a year for
the next three years.

                        Ariane Launch Delayed

	The first Ariane launch in over four months will be delayed
several more days to replace an electrical system on the booster,
Arianespace announced late Tuesday, August 3.

	An Ariane 42P was scheduled for launch Wednesday evening,
August 4, carrying the Indonesian Telekom 1 satellite into orbit.
Arianespace officials, however, decided to delay the launch less than
24 hours before the scheduled liftoff time when an electrical anomaly
was discovered in a third-stage engine for another Ariane booster
being tested in France.

	As a precaution, launch officials decided to replace the
electrical system for the Ariane 4 currently on the pad.  Arianespace
reported Thursday, August 5 that the launch had beed pushed back to
the evening of August 12.

	The last Ariane launch was more than four months ago, when an
Ariane 4 launched an Indian communications and weather satellite on
April 2.  Launches planned since then have been pushed back not
because of booster problems but by delays in the delivery of the
satellites to be launched on the boosters.  Only one other Ariane
launch has occurred in 1999, in February.

	Last month Ariane announced an aggressive new launch schedule
that called for eight launches of Ariane 4 and 5 boosters from the
beginning of August through the end of the year, to partially make up
for the delay.  This delay to replace the Ariane's electrical system
should only have a small affect on the schedule.

                    Chandra Approaches Final Orbit

	A successful thruster burn Wednesday afternoon, August 4,
brought the Chandra X-Ray Observatory close to its final elliptical
orbit around the Earth, project officials reported.

	The five-minute burn by Chandra's Integral Propulsion System,
starting at 12:36 pm EDT (1636 UT), raised the perigee, or lowest
point, of Chandra's orbit by about 2,210 km (1,370 mi.) to 5,690 km
(3,530 mi.)  The apogee of Chandra's orbit remained virtually
unchanged at 139,125 km (86,400 mi.).

	The successful firing also allayed concerns about the
telescope's thrusters, which were raised when a thruster burn on
Saturday, July 31 raised Chandra's apogee to about 139,100 km (86,380
mi.), 900 km (560 mi.) lower than planned.

	"While the propulsion system performed within specifications
and has delivered us to a completely acceptable apogee altitude, the
performance of Chandra's engine number 3 was slightly below
expectations," said program manager Fred Wojtalik.

	To prevent any possible future problems from the thruster,
telescope controllers switched to a redundant set of thrusters, which
were used for Wednesday's burn.  Because of the switch in thrusters
and time needed to reconfigure systems, the burn was pushed back from
early Monday, August 2, to Wednesday afternoon.

	"Initial indications are that today's firing went very well,"
Wojtalik said.  A fifth and final thruster burn took place on
Saturday, August 7.

	Chandra, launched by the shuttle Columbia on July 23, was
placed in an initial elliptical orbit by an Inertial Upper Stage.
The telescope has since used its own onboard thrusters to place it in
its final orbit, planned to be 10,000 by 140,000 km (6,200 by 86,940
mi.)  The slightly lower apogee Chandra currently has should not pose
a problem to the mission, officials said.

	Chandra is in such a highly elliptical orbit, which takes it
a third of the way to the Moon, to keep the telescope out of the
Earth's radiation belts for as long as possible in each orbit.

	The instruments on board the telescope are being turned on
and checked out while Chandra's orbit is tweaked.  That process has
been proceeding smoothly, Wojtalik said.

     Human Error Blamed for Recent Launch and Satellite Accidents

	Human error has been fingered as the root cause of both a
Titan 4 launch accident in April and a Global Positions System (GPS)
satellite that was damaged by rainwater in May, separate Air Force
investigations concluded last month.

	One investigation found that improperly developed and tested
software caused the failure of a Centaur upper stage during an April
30 launch of a Milstar satellite.  The software caused the Centaur
upper stage to lose all attitude control.

	In an attempt to regain attitude control, the Centaur used up
all its hydrazine propellant used for its reaction control thrusters.
As a result, the upper stage and the Milstar satellite were stranded
in a low, useless orbit.

	The findings confirmed earlier speculation that the problem
was caused by the control system of the Centaur and was not related
to its main engines.  The Centaur uses a version of the Pratt and
Whitney RL-10 engine that apparently exploded during a Delta 3 launch
just 4 days later.

	A separate investigation looked into how rainwater managed to
damage a GPS satellite on a Cape Canaveral launch pad in early May.
The satellite was atop its Delta 2 booster on the launch pad,
surrounded by the "White Room", a mobile structure that allows
technicians access to the satellite during launch preparations, when
a strong thunderstorm hit.

	The rainwater entered the White Room through a small leak in
the roof, and then pooled on a waterproof rain shroud hastily put
into place over the satellite.  The shroud could not support the
weight of the water, however, and collapsed, allowing water to spill
into the open satellite and damage it.

	Investigators found that technicians had not properly
assembled the shroud, taping together pieces on only one side of the
material and not both as required.  The leak in the roof of the White
Room contributed to the damage, investigators said, but the fact that
the room was not watertight was previously known.

	When the damage was discovered, the satellite has to be taken
back for repairs, which are estimated to cost $2.1 million.  No new
launch date has been set for the satellite.

	The accidents were two in a series of mishaps that stung the
launch industry earlier this year.  Three days before the Titan
4/Centaur failure, a Lockheed Martin Athena 2 failed to place a
commercial remote sensing satellite into orbit when its nose cone
failed to detach, making the payload too heavy to reach orbit.
Another Titan 4 launch failed in early April when the Inertial Upper
Stage designed to place an early-warning satellite into its proper
orbit misfired.  The results of that investigation have yet to be

         Scientists Salvage Useful Data from Failed Satellite

	A spacecraft launched earlier this year and all but written
off as a total failure has yielded important new scientific data
after all, a University of California Berkeley scientist reported
last week.

	Derek Buzasi, a research physicist at Berkeley's Space
Sciences Laboratory, managed to use a secondary instrument on the
Wide Field Infrared Explorer (WIRE) satellite to observe the
vibrations of another star for the first time.

	Buzasi used the 5-cm (2-in.) star tracker on WIRE to perform
a month's worth of observations on the star Alpha Ursa Major, or
Dubhe, and for the first time recorded the star's internal

	The star tracker was not designed for scientific observations
but rather to make sure WIRE was pointed in the proper direction for
its main instrument, an infrared camera mounted on a 30-cm (12-inch)

	However, an electronics glitch shortly after launch
jettisoned the spacecraft's sunshade prematurely.  The solid hydrogen
on WIRE, designed to keep the instrument cool, sublimated and vented
into space, spinning up the spacecraft.  By the time WIRE was brought
back under control, all the hydrogen had been lost, ending the main
scientific mission of the spacecraft before it could even begin.

	Buzasi, however, saw an opportunity to use WIRE's star
tracker for extended observations of stars.  He approached NASA and
received permission to use the star tracker.  Buzasi was the only
user of the spacecraft except for engineers conducting a series of
tests that have since concluded.

	"It's a really nice instrument," Buzasi said. "I was lucky
that WIRE retained the full capability of the star tracker and that
the CCD camera attached to it is better than most star trackers need.
And WIRE points amazingly well."

	Buzasi observed Dubhe for a month, looking for minute
variations in its brightness that would be caused by stellar
vibrations similar to ones seen in our own Sun.  Because the periodic
fluctuations in brightness are only about a thousandth the random
fluctuations caused by noise, he needed the long observing time to
detect the vibrations.

	Such observations could be conducted on Earth, but the
extended period of time needed to conduct them makes them
impractical, given the high demand for telescope time.  "A two-inch
aperture above the atmosphere can be better than ten meters below
it," Buzasi said.

	The observations of Dubhe have already allowed Buzasi and
colleagues to measure the mass of the star -- 4.25 times the mass of
the Sun -- more accurately than other means.  Later analysis should
provide insights into the interior structure of the star.

	Buzasi, who has access to WIRE's star tracker until October,
plans to observe the nearby star Alpha Centauri to search for
vibrations there.  "For us this is the most interesting star," said
Yale University's Pierre Demarque, a colleague of Buzasi. "We have
made lots of calculations about Alpha Centauri in hopes someday
someone would make these observations."

	Two satellites, the French COROT and the Canadian MOST, are
in development to perform similar studies, but won't be launched
until 2001.  "Derek has scooped both of them," Demarque said.

                       SpaceViews Event Horizon

August 11	Total solar eclipse visible in portions of Europe, 
		 the Middle East, Pakistan, and India.  (Partial 
		 phases visible in other areas, including 
		 northeastern North America.)

August 12	Ariane 4 launch of the Indonesian Telekom-1 
		 communications satellite from Kourou, French Guiana 
		 at 6:52 pm EDT (2252 UT)

August 12-15	Mars Society 1999 Conference, Boulder, CO

August 14	Galileo flyby of the Jovian moon Callisto

August 17	Delta 2 launch of four Globlastar satellites from 
		 Cape Canaveral, Florida at 12:37 am EDT (0437 UT)

August 18	Cassini flyby of Earth

August 22	Global Positioning System (GPS) week number rollover

September 23-26	Space Frontier Conference 8, Los Angeles, CA

                              Other News

SETI@home Approaches One Million:  The SETI@home project, where
people download screensavers to help process data collected in a
Search for Extraterrestrial Intelligence (SETI) effort, has now
nearly one million users.  During a Yahoo! chat July 30, project
director David Anderson and chief scientist Dan Wertheimer said that
almost 32 of 200 tapes, each holding 35 gigabytes (GB) of data, have
been processed since the project opened to the public in mid-May.
The number of people participating has surprised even the leaders of
the effort.  "We thought 100,000 [people would sign up], 150,000 if
we were lucky," Anderson said.

Io's Brilliant Aurora:  If an astronaut could survive the fierce
conditions on the surface of Io, the innermost of Jupiter's large
Galilean satellites, he or she would be dazzled by the brilliant
aurorae that would be visible.  Scientists using Galileo data have
found that Io is surrounded by red, green, and blue aurorae as
electrons accelerated by Jupiter's powerful magnetic field collide
with the moon's tenuous atmosphere.  The aurora in general tends to
fade when the Sun is eclipsed from view on Io by Jupiter, a sign that
the atmosphere partially cools and collapses during that time.  The
blue portion of the aurora actually grows brighter, though, as it is
caused by collisions with sulfur dioxide molecules emitted by
volcanic eruptions that are unaffected by the eclipse.

Asteroid Families: Groups, or "families", of asteroids that travel in
similar orbits usually have similar compositions, and thus are likely
remnants of a larger asteroid, an MIT researcher has found.  Schelte
Bus measured the spectra of over 1,000 asteroids, including those in
over a dozen families, and found that in nearly all cases the members
of the families had similar compositions.  "What this tells us is
that collisions are an important mechanism in the evolution of the
asteroid belt," Bus said. "Sometimes these collisions are powerful
enough to result in a catastrophic disruption, where the asteroid is
totally fragmented. This leaves families -- fragments of the original
parent asteroid -- traveling in similar orbits."

New Uranian Moons:  For the second time this year, astronomers have
discovered new moons around the planet Uranus.  An international team
of astronomers found two small moons orbiting the planet in mid-July.
This brings the total number of moons orbiting the planet to 20, more
than any other planet.  Astronomers found two moons orbiting the
planet in 1997 and discovered another earlier this year in old
Voyager 2 images taken during a 1986 flyby of the planet.  These five
moons are the only new moons to have been discovered around another
planet in the 1990s, although moons have been found around at least
two asteroids.

Antarctica and Europa:  Continued study of Lake Vostok, a large lake
buried beneath the ice of Antarctica, may help scientists better
understand the ice-covered oceans which are believed to exist on the
Jovian moon Europa and which may harbor life, scientists concluded in
an NSF report released last week.  Lake Vostok, about the size of the
Great Lakes' Lake Ontario, is buried under 4 km (2.4 mi.) of ice and
is thought to be a good terrestrial analog of the ice-covered oceans
thought to exist on Europa.  Scientists have proposed future
exploration of the lake, including drilling into the lake to retrieve
samples, as a way of learning more about the lake and learning how to
conduct future exploration of Europa.

Briefly:  Want some stardust?  Buy a diamond, advises a University of
Massachusetts geoscientist.  In a paper in the August 6 issue of
Science, Stephen Haggerty concludes that the carbon found in diamonds
comes directly from supernova explosions, and is not the result of
organic material exposed to the extreme heat and pressures within the
Earth, as previously believed.  The age of the carbon found in
diamonds and the similarity of carbon isotope ratios in diamonds with
those in meteorites led him to his conclusion... Professional
athletes often sign contracts that prevent them from taking part in
risky sports or other activities.  Soccer player Stefan Schwarz,
though, might the first pro athlete whose contract bans him from
space travel.  The English Sunderland soccer club added that proviso
to his contract in a recent trade after they heard that one of the
player's advisers had signed up for an unspecified commercial space
flight in 2002 and might bring the player along.  "At the end of the
day we are protecting the club, really," club chief executive John
Fickling told the BBC. "It was a little bit of a light-hearted moment
during protracted negotiations. But one day it could become be quite
acceptable to put such clauses in various contracts." 

                           *** Articles ***

                         The Early Explorers
                         by Andrew J. LePage


	In the chaos that swept the United States after the launching
of the first Soviet Sputniks, a variety of satellite programs was
sponsored by the Department of Defense (DoD) to supplement (and in
some cases supplant) the country's flagging "official" satellite
program, Vanguard.  One of the stronger programs was sponsored by the
ABMA (Army Ballistic Missile Agency) with its engineering team lead
by the German rocket expert, Wernher von Braun.  Using the Juno I
launch vehicle, the ABMA team launched America's first satellite,
Explorer 1, which was built by Caltech's Jet Propulsion Laboratory
(JPL)  (see "Explorer: America's First Satellite" in the February
1998 issue of SpaceViews).

	While these first satellites returned a wealth of new data,
they were limited by the tiny 11 kilogram (25 pound) payload
capability of the Juno I.  In order to orbit larger payloads carrying
a larger range of instrumentation, von Braun's team developed the
Juno II.  While the Juno I upper stage cluster of solid rocket motors
was retained, the Juno II used a modified Jupiter IRBM instead of the
smaller modified Redstone as a first stage.  This new combination was
first used to launch the Pioneer 3 and 4 lunar probes in December
1958 and March 1959 (see "Shooting for the Moon" in the January 1,
1999 issue of SpaceViews).

	ABMA planners started working with JPL under the aegis of
ARPA (Advanced Research Projects Agency) to develop new and larger
satellites to fly on the Juno II.  But long before the first of these
new satellites was even launched, political decisions changed the
landscape of America's fledging space program.  With the formation of
NASA in October of 1958, all ARPA-sponsored space science satellite
programs were transferred to the new space agency.  Among these
programs were the next generation of Explorer satellites the ABMA was

The First New Explorers

	The first of the new series of larger Explorer satellites was
the 39.7 kilogram (87.5 pound) satellite NASA designated as S-1.
Built by JPL, the spin stabilized S-1 consisted of a pair of
fiberglass cones joined at their bases with a diameter and height of
76 centimeters each.  The scientific payload consisted of instruments
to study cosmic rays, solar X-ray and ultraviolet emissions,
micrometeorites, as well as the globe's heat balance.  This was all
powered by a bank of 15 nickel-cadmium batteries recharged by 3,000
solar cells mounted on the satellite's exterior.  This advanced
payload was equipped with a timer to turn itself off after a year in

	Explorer S-1 was launched from Cape Canaveral on July 16,
1959 on Juno II Round AM-16.  Immediately upon launch an electrical
problem in the Jupiter first stage doomed the mission to failure.  In
one of the Cape's more spectacular early launch failures, the Range
Safety Officer detonated the rocket's destruct package 5.5 seconds
after launch after the rocket had pitched over towards the ground.  

	But as the ABMA team was preparing their next Juno II for
launch, another unrelated Explorer satellite would attempt to reach
orbit.  This satellite, called S-2, was originally a joint USAF-ARPA
project to launch a sophisticated probe into a very elongated orbit
to study the Earth's newly discovered Van Allen radiation belts.  S-2
would study this region in more detail than the Pioneer probes that
first traversed it.  Like the USAF-ARPA lunar Pioneer program, S-2
was transferred to NASA shortly after it was founded with the USAF
officially relegated to an advisory role.

	The S-2 payload was arguably one of the most advanced
satellites ever constructed up to that time.  Built by STL (Space
Technology Laboratory) like the USAF Pioneer orbiters (see "Operation
Mona: America's First Moon Program" in the April 1998 issue of
SpaceViews), the satellite was a 64 kilogram (142 pound) spheroid
with a diameter of 66 centimeters (26 inches) and a height of 74
centimeters (29 inches).  The spin stabilized satellite used four
extendable solar "paddles" to power its array of onboard equipment. 
	The impressive array of instruments was designed to study
various types of trapped radiation, galactic cosmic rays,
geomagnetism, radio propagation and micrometeorites.  Also carried
was a TV line scanner similar to that flown on the USAF Pioneers
designed to produce crude images of the Earth from orbit.  These TV
signals were transmitted back to Earth along with digital data from
other instruments using a UHF transmitter that operated for a few
hours a day.  A pair of continuously operating VHF transmitters
returned a constant stream of analog instrument data.  The S-2
payload would be sent into its elongated 12-hour hour orbit using the
USAF Thor-Able - the same launch vehicle unsuccessfully used to send
the USAF Pioneers to the Moon.

	Thankfully, S-2 would have better luck than the Pioneers
orbiters.  On August 7, 1959 (40 years ago this month) Thor-Able 3
successfully placed S-2, now officially designated Explorer 6, into a
245 kilometer (152 miles) by 42,400 kilometer (26,343 mile) orbit
inclined 47 degrees to the equator.  The only major problem occurred
when one of the four solar paddles failed to fully extend resulting
in the new satellite generating only 63% of nominal power.  This
amount gradually decreased through the mission and affected the
quality of the transmitted signal especially near apogee.

	Despite its initial problems, Explorer 6 was a spectacular
success.  It returned the first crude images of the Earth from orbit.
It also supplied a wealth of fresh data on the radiation and magnetic
environment of near-Earth space.  On September 11 one of the two VHF
transmitters failed and contact was finally lost on October 6 when
the power levels fell below the minimum the satellite needed to
operate.  In total, Explorer 6 returned 23 hours of digital data and
827 hours of data in analog form.  Experience from the design of the
successful and innovative Explorer 6 would be used by STL engineers
for later Pioneer lunar and interplanetary probes.

Success for ABMA

	With Explorer 6 in orbit, the ABMA team was ready for another
launch attempt.  Juno II Round AM-19B carried a USAF-developed
payload called Beacon.  This was a 12 kilogram (26 pound) balloon
designed to inflate to 3.7 meters (12 feet) across once in orbit.  It
was meant to study the properties of the upper atmosphere from orbit.
A malfunction in the rocket's guidance system shortly after launch on
August 14, 1959 (40 years ago this month) prevented Beacon from
reaching orbit.  

	Undeterred, von Braun's team studied the causes of the Juno
II failures and made corrections for the launch of the next satellite
designated S-1a on Round AM-19A.  Payload S-1A weighed 41.9 kilograms
(92.3 pounds) and was a slightly improved version of the ill fated
S-1.  But unlike S-1, S-1a was successfully launched into a 557
kilometer (346 mile) by 1,069 kilometer (664 mile) orbit inclined
50.3 degrees to officially become Explorer 7.  NASA's newest Explorer
returned much new information on the spatial and temporal structure
of the inner edge of the Van Allen radiation belts that complimented
earlier data and that taken concurrently by later satellites.
Explorer 7 returned continuous real-time data through February 1961
and then intermittently until August 24 of that year.

	Next up was payload S-46.  This 10.2 kilogram (22.5 pound)
cylindrical satellite was 18 centimeters (7 inches) in diameter and
53 centimeters (21 inches) long.  Similar in design and mission to
the earlier Explorer satellites launched by the Juno I, S-46 carried
instruments to study the Earth's radiation belts.  But unlike its
earlier siblings, S-46 also carried four banks of solar cells mounted
on a rectangular box to recharge its batteries for up to one year.
By using the more powerful Juno II, this new payload could survey the
Van Allen belts from a more highly elongated orbit that was designed
to survey its breadth.  The new payload mounted atop of Juno II Round
AM-19C was launched on March 23, 1960 but all telemetry was lost
shortly after first stage burn out.  The Juno II had failed again.

	The next attempt by ABMA to launch a JPL-built Explorer came
later that year.  Payload S-30 was similar in shape and design to the
earlier S-46-series satellites except it did not carry solar cells
and had a life of only 1.5 months.  Weighing in at 40.26 kilogram
(88.65 pounds), this satellite was designed to make in situ
measurements of upper atmospheric properties such as electron
density, temperature, composition and how they vary with time and
altitude.  The solar cells were excluded from this payload because
asymmetric charging on the cell surfaces would produce electric
fields that could affect experiment results.  Three different sensors
to measure micrometeorites were also carried.  

	This new payload was successfully launched into a 459 by
2,289 kilometers (285 by 1,423 mile) orbit on Juno II Round AM-19D on
November 3, 1960.  As expected, Explorer 8 operated until December 28
when its batteries were finally exhausted.  During its useful life,
Explorer 8 returned a large volume of data but unfortunately there
were problems processing the raw telemetry into usable measurement.
Because of these problems, most of the data had to be processed by
hand.  Nonetheless many important new observations were made
including the discovery of a helium layer in the ionosphere.

The Last Flights of the Juno II

	From the start NASA policymakers knew that the Juno II was
only a stopgap measure.  Kludged together from a variety of
preexisting hardware, the Juno II was hardly an optimum design for
the task of satellite launches.  And its high failure rate only
underscored the need for a replacement.  By the end of 1960, the all
solid-rocket motor Scout had already started test flights.  Promising
lower costs and better reliability, the Scout was designed to launch
small Explorer-class payloads into low orbits and would gradually
replace Juno II in that role during 1961.  Larger payloads to be
launched into distant Earth orbits would use a highly upgraded
version of the Thor Able called the Thor Delta (later know as just
Delta).  But in the mean time the remaining Juno II rounds had
payloads to launch.

	The next payload ready for launch was S-45.  It was similar
to the proven design of Explorers 7 and 8 and weighed 34.1 kilograms
(75.0 pounds).  This solar-powered satellite would transmit low
power, phase-coherent signals at six different frequencies between 20
and 960 MHz which would be monitored by ground stations.  This
allowed scientists to determine many key parameters of Earth's
ionosphere.  On February 24, 1961 what would have become Explorer 10
(Explorer 9 was successfully launched on a Scout eight days earlier)
was launched on Round AM-19F.  Unfortunately a malfunction prevented
the last two stages from igniting and S-45 failed to reach orbit.  

	Unlike the earlier Explorers, payload S-15 observed the
heavens making it the first astronomical satellite.  This satellite
consisted of an octagonal box 31 centimeters (12 inches) across and
59 centimeters (23 inches) long mounted on top of a 52 centimeter (20
inches) long cylinder with a diameter of 15 centimeters (6 inches).
The principle instrument was designed to detect gamma rays with an
energy greater than 50 Mev over a field of view of five degrees.  The
spin of the satellite in orbit would allow this directional detector
to scan most of the celestial sphere with emphasis along the galactic
plane.  The satellite would also measure the Earth's reflectivity to
gamma rays.  This 43.2 kilogram (95.1 pound) satellite had a life
expectancy of four months due to the deleterious effects of radiation
on the solar cells mounted on the exterior of the box.

	Launched on April 27, 1961, S-15 became Explorer 11 when
Round AM-19E sent it into a 497 by 1,793 kilometer (309 by 1,114
mile) orbit.  Despite the loss of its tape recorder, Explorer 11 was
able to return a large amount of real-time data during its
unexpectedly long 224 day life.  One of the more important findings
was the lack of evidence to support steady state cosmology.  This
theory proposed that new matter was being continuously created to
fill the expanding Universe.  This process should have generated a
gamma ray signature that Explorer 11 could detect.  Their absence was
a boost for the popular alternative theory called the Big Bang.

	The last payload that Juno II launched was S-45a.
Essentially a duplicate of the unsuccessful S-45, the last ABMA-JPL
Explorer lifted off on Round AM-19G on May 24, 1961.  But failure
struck again when a malfunction during second stage ignition doomed
the mission.  With this anticlimactic finale, the Juno II was quietly
retired after ten launches.  While the Juno II had its problems, it
did successfully launch three satellites and one lunar probe that
added immensely to the first steps in the exploration of space.  


Josef Boehm, Hans J. Fichtner, and Otto A. Hoberg, "Explorer
Satellites Launched by Juno 1 and Juno 2 Space Carrier Vehicles", in
Aeronautical Engineering and Science, Ernst Stuhlinger, Frederick I.
Ordway III, Jerry C. McCall, and George C. Bucher (editors), pp.
218-239, McGraw-Hill, 1963

Ray V. Hembree, Charles A. Lundquist, and Arthur W. Thompson,
"Scientific Results from Juno-Launched Spacecraft", in Aeronautical
Engineering and Science, Ernst Stuhlinger, Frederick I. Ordway III,
Jerry C. McCall, and George C. Bucher (editors), pp. 281-297,
McGraw-Hill, 1963

Bill Yenne, The Encyclopedia of US Spacecraft, Exeter Books, 1985

Major NASA Launches, PMS 031 (KSC), NASA, December 1989

Drew LePage is a physicist and freelance writer specializing in
astronomy and the history of spaceflight. He can be reached at

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